Process for producing a crimped multifilament yarn



March 11, 1969 J. J. MERTENS 3,431,716

PROCESS FOR PRODUCING A CRIMPED MULTIFILAMENT YARN Filed Sept. 27, 1965 I NVEN TOR.

JOHAN J. MERTENS Y j w; 0W

ATTQRNEY United States Patent 3,431,716 PROCESS FOR PRODUCENG A CRIMPED MULTIFILAMENT YARN Johan J. Mertens, Rozendaal, Gelderland, Netherlands, assignor to American Enlra Corporation, Erika, N.C., a corporation of Delaware Filed Sept. 27, 1965, Ser. No. 490,360 Claims priority, application Netherlands, Get. 16, 1964, 6412050 US. Cl. 5734 Claims Int. Cl. D0111 13/26;l)02g 3/02; Dtlzj 13/00 ABSTRACT OF THE DISCLOSURE Process and apparatus for manufacturing multifilarnent yarn having a low elasticity and an attractive and uniform crimp. The invention is directed to a continuous treatment process wherein yarn is successively heat-set while temporarily in a state of high twist, allowed to relax and then passed to a stabilization zone while in the twisted state, with the temperature of the stabilization zone increasing linearly from the point of the yarns entry into the zone and to the point of yarn exit from the zone.

The present invention is directed to an improved process and apparatus for manufacturing a multifilament yarn having a low elasticity and an attractive and uniform crimp. More particularly, the invention relates to a continuous treatment process whereby the yarn is successively heat-set while temporarily in a state of high twist, allowed to relax, stabilized while in a crimped state, and finally wound.

In prior art processes of the above type, stabilization of the crimped yarn merely implies heating the yarn to a predetermined final temperature. This stabilization treatment is carried out by guiding yarn in a relaxed state over a plate or roller heated at a constant temperature. The crimped yarns obtained by such processes have properties that are different from those of the generally known elastic yarns obtained by the false twisting process. In the manufacture of the latter type of yarns, the heatsetting treatment of the yarn in a state of high twist is not followed by an additional heat treatment, and the resulting yarns, therefore, not only possess crimp but also a high elasticity. The yarns to which the invention relates, however, have an attractive crimp, but a low elasticity.

When the stabilization processes in the prior art are carried out under a constant temperature, the heat gradually penetrates toward the center of the yarn and causes the stiffness of the component yarn filaments to vary from point to point. This variation causes the internal stresses in the filaments to also vary and such latter variation will often cause the crimped yarn to assume a Shape in which the potential energy of the yarn is at all points at a minimum. This shape is often not in accordance with that of the ideal crimp.

It has been found that a considerably more attractive crimp may be imparted to these low elasticity yarns if the stabilization treatment is carried out by heating the yarn at a temperature which increases through the stabilization zone in such a manner that the yarn is given a predetermined temperature and speed from point to point while passing through said stabilization zone. By subjecting the yarn to a controlled, point to point temperature 3,431,716 Patented Mar. 11, 1969 gradient while passing through the stabilization zone, the yarn builds up resistance to the heat, becomes more uniformly heated, and may be prevented from overheating. In this manner, the variation in the internal stresses of the yarn filaments is held at a minimum and the yarn will assume a shape which more nearly approaches the ideal crimp shape.

For carrying out the above process, use is made of an apparatus which comprises a yarn supply system which feeds the yarn successively into a heat-setting apparatus, a false twisting member, a relaxation system and a stabilization apparatus. The last mentioned apparatus comprises a rotatable roller with a heating system therein for imparting to the roller a temperature which increases in the axial direction thereof. The roller contains a number of circumferential grooves over which the yarn passes, and these grooves are heated at increased temperatures axially of the roller in order to insure that the yarn is heated over a predetermined temperature gradient throughout the stabilization process.

Finally, the invention includes the crimped yarns manufactured by the above described process and using the above described apparatus.

Accordingly, it is an object of the present invention to provide new and improved method for producing a multifilament yarn having a uniform and attractive crimp while possessing a low elasticity.

It is another object of the invention to provide a new and improved apparatus for carrying out the above described method.

It is a further object of the invention to provide an improved multifilament yarn having a uniform and 'attractive crimp while possessing a low elasticity.

These and other objects of the invention will become more fully apparent in the following detailed description of the annexed drawing.

Referring in detail to the drawing, there is shown a yarn supply package 1 from which yarn 2 passes through a thread eyelet 3 at a speed which is imparted to the yarn by yarn feed system 4. This yarn feed system consists of a known system of driven rollers and pressure rollers between which the yarn 2 is passed. A similarly constructed yarn delivery system is indicated by the reference numeral 5.

Between the feed systems 4 and 5 the yarn is passed through a heating tube 7 to a false twisting member 6. From the false twisting member 6, the yarn is passed through the delivery system 5 to a roller 8 having a number of circumferential grooves thereon. The turns of the yarn 2 in the grooves of the roller 8 are kept separated by means of an idler 9, the idler 9 and roller 8 being slightly out of parallel in two separate planes to insure that the turns of yarn are kept separated. After the yarn has left the roller 8, it is collected on a package 10.

The package 10, which is mounted on a spindle, is freely rotatable and driven at a constant speed by a roller 11. While the yarn is being collected on the package 10, it is caused to traverse as schematically indicated by the arrows.

The temporary high twist which is inserted into the length of yarn between the yarn feed system 4 and the false twisting member 6 by said false twisting member 6 is set in the heating tube 7. When the yarn leaves the delivery system 5, it is highly elastic as a result of this heat-set and will develop crimp upon contraction.

The roller 8 and the idler 9 are driven at a peripheral speed which is considerably lower than that of the yarn delivery system 5. This makes it possible for the yarn to crimp before it runs onto the roller 8. The crimped yarn is stabilized on the roller 8 and to this end roller 8 is heated by electrical heating members (not shown) which are mounted in the interior of the roller. The roller 8 is heated so that the temperature from left to right increases about 80 C., and the speed at which the yarn is taken up by the package 10 is substantially equal to the speed at which it is passed over the roller 8.

For the purpose of obtaining a satisfactory crimp shape there are many conceivable combinations of ways in which the yarn stabilization temperature and yarn speed may be varied. However, according to the present invention it is preferred that during the stabilization of the crimped yarn the temperature of the yarn be increased linearly and that the yarn speed remain constant during its passage through the stabilization zone,

It has been found that if the temperature at which the temporary high twist is heat set is chosen as low as possible, a yarn may be obtained which shows a satisfactory crimp and hardly any elasticity. Following this teaching the temporary high twist may set to a degree which is just high enough to allow the yarn to fully develop its crimp just before it enters the stabilization zone, but still sufliciently high to permit complete reorientation of the molecules during the stabilization phase. Thus, when the yarn is about to be wound on a tube it will be substantially free from internal stresses.

Controlling the yarn speed during stabilization may be done in several ways. For instance, the stabilization zone may be divided into a number of short zones which are separated from each other by pairs of driven nip rollers. According to the invention, however, a constant yarn speed is to be preferred during stabilization and the yarn 5 is passed at a constant speed in the plurality of turns around the grooved roller 8 as shown. By choosing the number of turns (and grooves) around the roller 8 sufficiently high, it has been found possible to prevent any slippage of the yarn in the longitudinal direction over the roller surface. When relatively narrow grooves are cut on the roller 8 they enhance the heat transfer from the roller surface to the yarn.

The diameter of the roller 8 may be changed in an axial direction, resulting in a cone or cone-frustum shaped roller. As a result of such change the speed of the yarn may be changed as it passes axially down the roller. It has been found, however, that by using a simple cylindrical grooved roller, a satisfactory crimp shape may be obtained if the temperature of the roller increases axially in a linear fashion. If, for example, the present process is applied to a polyamide yarn, then a stabilization temperature should increase linearly from approximately 100 C. to 180 C.

The following examples illustrate the conditions under which the process according to the present invention has been carried out.

EXAMPLE I A melt-spun polyethylene terephthalate yarn composed of 96 filaments and having a denier of 150 was guided through the false-twisting zone at a speed of 70 meters/ minute. A false twisting spindle of the belt-driven type was used and operated at a speed of 140,000 rpm. The heating tube 7 was heated to 160 C.

The roller 8 was 20 cm. in diameter and 20 cm. in length and was provided with 12 grooves. The circumferential speed of the roller was set at 50 meters/minute and the roller temperature was approximately 100 C. at the point of arrival of the yarn and approximately 180 C. at the point of yarn leaving. The yarn was wound onto the package at a speed which was substantially equal to the speed at which it was passed around the roller 8. The yarn obtained possessed great uniformity, an attrac- The false-twisting member used in this case consisted of two facing, flat discs rotating in opposite directions. The discs were mounted at a small angle relative to each other and their axes were displaced relative to each other in a radial direction. When the yarn was passed between the discs it was simultaneously forwarded and false twisted. The yarn used was one having a basis of polyaminocaproic acid; it was composed of 63 filaments and had a denier of 1140. This yarn was passed through the false-twisting zone at a speed of 20 meters/minute and was given a false twist of 950 turns per meter.

The temperature of the heat-setting apparatus was approximately C., and the roller 8 was driven at a peripheral speed of 150 meters/minute. From the point of arrival of the yarn on roller 8 to the point of leaving, the temperature of the roller increased from 100 C. to C.

The yarn was guided around the roller 8 in 15 turns and the yarn thus obtained was very suitable for the use in the manufacture of carpets.

It should be understood that the present invention is by no means limited by the specific illustrated examples of actual reductions to practice of the invention embodied in the novel apparatus and process described hereinabove. It should be further understood that various modifications may be made in said process and apparatus without departing from the spirit and scope of the invention. Accordingly, said invention is limited only by way of the following appended claims.

What is claimed is: 1. In a process for manufacturing a crimped multifilament yarn wherein the yarn is successively heat-set while temporarily in a state of high twist, allowed to relax to a crimped state and passed through a stabilization zone the improvement comprising progressively heating the crimped yarn in the stabilization zone by continuously increasing temperature in the zone from a point where the yarn enters the zone to the point where the yarn leaves the zone.

2. The process according to claim 1 wherein (a) said yarn passes through said stabilization zone at a constant speed, and

(b) the temperature in the zone increases linearly from the point of yarn entry into said zone to the point of the yarns exit from said zone.

3. The process according to claim 2 wherein the temperature applied to said yarn to give it a temporary high twist is just high enough to allow said yarn to fully develop its crimp before entering the stabilization zone.

4. A process for manufacturing yarn having an attractive and uniform crimp while exhibiting a low elasticity comprising the successive steps of (a) heat-setting said yarn while temporarily in a state of high twist,

(b) removing all tension and stress from said yarn to allow it to relax to a crimped state,

(0) feeding said yarn through a stabilization zone, and

(d) heating said yarn in said stabilization zone by progressively increasing the temperature in the zone from a point of the yarns entry into said zone to a point where the yarn leaves said zone.

5. The process according to claim 4 wherein (a) said yarn passes through said stabilization zone at a constant speed, and

(b) the temperature of the stabilization zone increases linearly from the point of yarn entry into said zone to the point of yarn exit from said zone.

6. The process according to claim 5 wherein the yarn is heat-set while temporarily in a state of high twist at a temperature high enough to enable said yarn to fully develop crimp and still be capable of having the molecules thereof completely reoriented during stabilization.

7. The process according to claim 6 wherein said yarn is a polyamide which is heat-set at a temperature between 149 C. and 161 C.

8. The process according to claim 6 wherein said yarn is a polyamide which is heated in said stabilization zone at temperatures which increase linearly from approximately 100 C. to approximately 180 C.

9. Apparatus for manufacturing a crimped yarn having a low elasticity and an attractive and uniform crimp comprising (a) yarn supply means,

(b) means adjacent said yarn supply means for false twisting yarn from said yarn supply means and means for heat setting said yarn while temporarily in a state of high twist,

(c) means for relaxing the yarn which is temporarily in a state of high twist,

((1) means for passing the relaxed yarn through a stabilization zone, and

(e) means for continuously increasing the tempera- 20 ture in said stabilization Zone at a point of yarn entry into said zone to a point of yarn exit from said zone. 10. Apparatus of claim 9 wherein said heating means includes (a) a roller having circumferential grooves therein over which said yarn may be passed and heated, said said roller to an adjacent groove in said roller.

References Cited UNITED STATES PATENTS Gilchrist et a1. 57--34 XR Enneking 57--34 De Moncuit et a1. M 5734 Fitton et al 57-34 XR Scragg 5734 Loftin et a1. 57-157 XR Nava 5734 XR FOREIGN PATENTS Belgium. Great Britain. Great Britain.

U.S. Cl. X.R. 

